Differential pressure sensors are a critical part of most mechanical and electromechanical devices that require the precise measurement of air, gases or liquids to determine the comparative difference between two inputs.
For example, if there is a valve in a pipe, a differential pressure sensor will measure the pressure on both sides of the valve. If the pressures do not match, then it signals that either the valve is not fully open or there is a potentially serious issue (such as a blockage).
Differential pressure sensors are a key element in many devices, such as medical ventilators, spirometers, anesthesia devices, industrial flow meters and HVAC systems.
While some variation in differential pressure sensing has existed for hundr years, today’s modern pressure sensors can trace their roots back to the late 1960s when Honeywell applied for the first patents in piezoresistive silicon sensor technology.
Over the pursuant decades, the technology has been improved by further integrating electrical and mechanical components that are manufactured using silicon processes similar to integrated circuits. This process is known as Microelectromechanical Systems or MEMS.
Today’s devices, whether it be consumer electronics such as smartphones, medical equipment such as respirators or industrial ventilation systems, have become much more intelligent. But not all components have advanced.
Critical to many applications, differential pressure sensors have changed little over the past several decades. This has resulted in product designers having to put together piece-meal solutions that are often not performance-optimized and usually extend product development timelines.
Applications
Differential pressure sensors are used in a variety of applications across a broad range of industries. While the list of uses is endless, for this article we will list some of the more common uses in the medical, industrial and HVAC industries.
Medical Applications
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Here are some of the more common medical applications for differential pressure sensors:
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Ventilators: Multiple differential pressure sensors are found in ventilators to ensure each channel is supplying the correct amount of air/gas, the right mix of air and gases are being administered, the right inflow is going to the patient and the patient’s air outflow is at appropriate levels.
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Spirometers: Differential pressure sensors are used in spirometry to accurately measure a patient’s lung capacity and volume under various test conditions. These results help diagnose if there is lung disease present, and if so, what type.
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CPAP/BiPAP: Differential pressure sensors are utilized in CPAP and BiPAP devices such as sleep apnea machines and nebulizers. They ensure the right mix of air/gas is going to the lungs and monitor to ensure the patient is breathing properly.
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Anesthesia Machines: Differential pressure sensors ensure the right dosage of anesthesia is administered to a patient.
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Oxygen Concentrators: Differential pressure sensors monitor the flow of oxygen to ensure the patient is receiving the correct amount of oxygen and is breathing properly.
Industrial Applications
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The list of industrial applications for differential pressure sensors is quite long. Here is a partial list of how to utilize differential pressure sensors in these applications:
- 3D printing: Ensuring the printer’s output matches the input.
- Auto smog testing: Verifying that pollution levels are within acceptable parameters.
- Aviation instrumentation: Continually verifying that instrumentation readings are accurately reflecting the performance of mechanical devices such as wing positioning, cabin pressure, as well as the performance of hydraulic brakes and engines.
- Chemical monitoring: Verifying that chemical levels are within acceptable parameters.
- Device calibration: Making sure that lab and manufacturing equipment are calibrated to their proper levels before and during process work.
- Environmental chambers: Ensuring chambers are functioning correctly and are properly sealed.
- Leak testing: Measuring differential pressure to determine if there is a leak in the system.
- Nuclear power monitoring: Monitoring pressures in a nuclear power plant to avoid potential radiation exposure.
- Particle counting: Accurate counting of various particles in air or within a system.
- Pneumatic system monitoring: Monitoring hydraulic pressures to ensure proper system operation.
- UAV/UAS (drones): Verifying engine performance and that the altitude and direction accurately reflect the commands given to the drone.
- Water quality testing: Ensuring various chemicals in water are not exceeding acceptable levels.
HVAC Applications
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Like industrial applications, the list of HVAC applications is also quite long. Here is a partial list of how to utilize differential pressure sensors in HVAC:
- Air filter monitoring: Monitoring the efficacy of air filters to notify personnel of when to clean or change a filter.
- Air handler: Monitoring the efficacy of air handlers and blowers to ensure the air flow is as intended – helps reduce energy cost by eliminating inefficiencies in the HVAC system.
- Air pressure monitoring: Monitoring changes in air pressure.
- Air quality testing: Ensuring the air we breathe is not contaminated beyond acceptable levels.
- Automated safety systems: Act as a switch to automatically turn devices on or off depending on the differential pressure measurements.
- Clean room access: Ensuring that dust levels do not exceed the requirement for a clean room in R&D or manufacturing.
- Hospital room monitoring: Monitoring a hospital room to ensure the air quality meets acceptable parameters.
System-in-a-Sensor: Utilizing SoC Concepts to Transform Sensors
System-on-a-Chip (SoC): The Drive to Reduce Power, Cost and Size
The integration of many components onto a single die revolutionized the consumer electronics industry. Instead of each feature having its own integrated circuit (IC), a system-on-a-chip IC integrates these distinct functions on a single die or substrate in order to reduce power, shrink the size and lower the cost of a product.
The first SoCs date back to the 1970s when many components were integrated into single chips to control the nascent digital watch market. This allowed the watches to be smaller in size and provide sufficient battery life.
After watches, calculators started integrating new SoCs that made the devices lighter and substantially cheaper. By the 1990s, IC companies started embedding microcontrollers with DSPs and other components into system-level chips that drove the rapid adoption of handheld devices (games, instruments, phones), peripherals and other products.
By taking the IC with the most intelligence, integrating it with other components and sharing its intelligence across these additional functions, the electronics industry entered a new era of inventiveness.
Today, SoCs are in most electronic products from smartphones, TVs and automobiles to IoT devices and embedded systems. The ability to integrate many functions onto a single chip has led to an explosion of highly powered devices throughout all segments of the electronics industry, benefiting our daily lives.
The SoC concept is now expanding to other products that will drive the next wave of innovation, such as sensors.
Figure 1. SoC – Smartphone AP Example. Image Credit: Superior Sensor Technology
System-in-a-Sensor: Bringing SoC Concepts to Sensors
As most sensors detect or measure physical properties, they have not been integrated into ICs. Acting as a bridge between the analog and digital worlds, and often being location dependent, has made adding their full capability into an integrated circuit that sits on a centralized PCB extremely difficult.
However, as a standalone sensor module, we can utilize the SoC concept in creating a new generation of sensors that are more efficient, reliable, flexible and functional.
Like SoCs, smart sensors are not a new concept. In fact, these integrations started in the 1970s in advanced IR surveillance and warning systems.
Originally commissioned by the military, the advances in computing power, component miniaturization and software algorithms are now opening up new doors for advanced sensor modules across industries and applications.
Integrating a microcontroller or DSP in the sensor module gives it the intelligence to offer additional capabilities such as self-calibration, self-identification, digitization of sensor data and wireless communications.
Today, smart sensors are everywhere, including homes, automobiles and factories.
We have all experienced situations where a motion sensor drives lighting and/or the HVAC in a building, a distance sensor turns a camera or spotlight on and off, a water/humidity sensor instructs a sprinkler system to turn on, and an alarm sensor that sends a wireless notification in case of a breach.
This is accomplished by having the base sensor(s) directly interact with a microcontroller or DSP and a communications module. An integrated smart sensor solution is designed to work better than trying to piece-meal all the components together.
The tighter integration reduces latency, better utilizes system resources and increases overall performance.
Figure 2. Smart Sensor Example. Image Credit: Superior Sensor Technology
Taking it a step further, the new System-in-a-Sensor concept brings advanced capabilities that are application or use-case specific and can be adjusted even after a sensor is deployed in the field.
Much like a smartphone’s usage pattern is controlled by a user, a system-in-a-sensor’s usage pattern can be controlled either by an operator or based on system or external events.
Parallels with the Evolution of Smartphones
Most of the computing functions in a smartphone are driven by an application processor (AP) – an extremely intricate SoC controlling many of the functions of the phone including the display, applications, power and communications modules.
The AP is very intelligent, depending on what you are trying to do with the smartphone, the SoC ‘structures’ itself to optimize the performance for the desired function.
It is like a swiss army knife – depending on what you are trying to do, it pulls out the right tool so you can do it as efficiently as possible. Sensors should essentially have this same level of ingenuity.
As many sensors are powered by ASICs, microprocessors, controllers or DSPs, they can be architected to be flexible and intelligent to optimally perform different functions like an AP does on a smartphone.
Having one sensor that can be integrated into many devices and then configure itself based on the immediate need is the future of sensor technology.
This can be seen in the NimbleSense architecture deployed in Superior Sensor Technology's pressure sensor products.
One sensor can support a wide array of pressure ranges without any degradation in accuracy, and various features can be turned on and off depending on the application for its use.
System-in-a-Sensor: Benefits
Bringing intelligence into a system-in-a-sensor implementation can provide lots of benefits. For example, by procuring the same system-in-a-sensor for numerous projects, you gain the benefit of lower inventory costs, simplified manufacturing and a more straightforward supply chain.
Manufacturers will only need to worry about building and creating an inventory of one system. This lowers inventory costs and simplifies manufacturing as the production lines do not need to be reconfigured for each product.
Furthermore, using one sensor for multiple purposes and projects, supply chain complexity can significantly be reduced by procuring a single part. The benefit of economies of scale is also provided as businesses start to ramp up.
In addition, a sensor can be configured ‘on the fly’ to support various applications and features. This enables engineers to design their products more rapidly by integrating the same sensor in many devices and applications.
Development cycles will be shorter, and engineers can freely optimize their design throughout the development phase without the risk of having to change to a new component that can possibly cause production delays.
Finally, overall system performance is enhanced due to the customizable capabilities of the system-in-a-sensor.
If architected correctly, like a smartphone AP, the sensor will ensure peak performance across many use cases.
This is due to the sensor being optimized for flexible general use (e.g., supporting multiple pressure ranges while maintaining the same levels of accuracy) and having the ability to turn on specific features for certain applications.
Like an SoC, the system-in-a-sensor is designed to operate at maximum capability across a wide array of applications and configurations.
Moreover, a company can quickly bring out derivatives to expand product lines and further segment its offerings since one sensor solution can be deployed to support many different products.
For more details about the full capabilities of a System-in-a-Sensor solution, please download the NimbleSense white paper.
This information has been sourced, reviewed and adapted from materials provided by Superior Sensor Technology.
For more information on this source, please visit Superior Sensor Technology.